Process for separation of mineral oil



April 4, 1939.

M. H. TUTTLE PROCESS FOR SEPARATION OF MNERAL OH,

Filed Ju1y-2o, 1952 Patented Apr. fl, 1939 PATENT OFFICE 2,153,353PROCESS FOR SEPlTION F MINERAL Malcolm H. Tuttle, New Rochelle, N. Y.,asslgnor to Max B. Miller & Co., Inc., New `York, N. Y., a corporationoi' Delaware Application July zo, 1932, serial No. 623,483

s claims. (cl. 19o-1s) This invention relates to an improved process ofseparating mineral oil stock, by means of solvents, into a paraiiinictypeiraction, suitable for use as a lubricating oil, and anon-parafilnic or naphthenic type fraction.

'Mineral oil stocks are physical mixtures of a variety of so-calledparailinic hydrocarbons and a number of types of non-parailinichydrocarbons whichare generally referred to in the art as naphthenicoils. These naphthenic oils comprise a variety of compounds 'some ofwhich are aromatic, some asphaltenes, some unsaturated, some naphthenic,and some heterogeneous. v

It has been proposed to divide mineral oil into iiiv 'fractionsrespectively more paramnic and more naphthenic than the original oil byphysically treating or extracting the oil with solvents (e. g.nitro-benzene) having a greater solvent power for naphthenicconstituents than for parafiinic constituents, the mixture separating bygravity into an upper layer comprising the more paraiiinic fraction anda lower layer comprising the more naphthenic fraction dissolved in thesolvent. Complete separation of naphthenic from parailinic constituentshas not been achieved and the lower layer contains a substantialproportion of paraflinic constituents.- Treatment of mixed 'base oils oflow asphalt content by such procedure has produced oil having morepronounced parailinic characteristics than on produced by acid treating;but

separation of residual oils of high asphalt content, by the use ofselective solvents heretofore proposed, has proved impracticable orfailed. The solvents proposedy appear` to be miscible in substantiallyall economical proportions with residual oils of high content ofnaphthenic constituents or asphalt, and the necessary separation intolayers does not occur. It' appears that the solventsle: g.nitro-benzene) form with the 40 asphalt' and/or with the naphthenicconstituents a mixture having extensive solvent power for parainicconstituents. Solvents having more limited solubility for naphthenicoils may cause a separation into naphthenic and parafilnic layers,presumably because such solvents do not lform with asphalt or naphthenesa mixturehavingsubstantialsolvent power for parailins, but no suchsolvent is known which will produce from residues of Mid-Continent oilsof high as- '50 phalt content an oil having characteristics comparableto the characteristics of Pennsylvania oils.

To assist .in understanding the eiects. and resuits o! the practice ofthis invention, reference maybe made to certainarbitrary values com- 5monly employed to indicate the nature of oil. For example, parafllnicoil has a lower specic gravity for a given viscosity than doesnaphthenic oil and the relation o! viscosity to speciilc gravity isindicated by the viscosity-gravity constant de- 10 termined inaccordance with the following equation. f

a=viscositygravity constant.

V'=Saybolt viscosity at 210 F.

G==speciilc gravity at F. Pennsylvania lubricating oils have aviscositygravlty constant falling between approximately .807 and .827;mixed base Mid-Continent lubricating oils have a viscosity-gravityconstant falling approximately between .827 and .867; and naphthenic orasphalt base lubricating oilsfrom the Gulf coast and California have aviscosity- 25 gravity constant falling approximately between .867 and.887. However, speciilc oils from one field will have aviscosity-'gravity constant fallingl within the range above given foranother ileld. Moreover, the relation o! temperature to viscosity ismeasuredlby a viscosity index in which Pennsylvania oils have a value ofto 100 and oils of lower viscosity index are less paraftlnic andthe oilsof higher viscosity index are more paramnic. u

Herein naphthenic oils or particularly high melting point are referredtoas asphaltic oil or "asphalt" Solvents for naphthenic constituentsvary in their properties. One class of such solvents, of 4 whichnitrobenzene is an example,.is made up of solvents which are miscible inall proportions with `mixed base mineral oil of high asphalt content,although they are highly selective withrespect to naphthenicconstituents when parainic constituents are present'in predominatingproportion. For example, while nitrobenzene takes up naphthenicconstituents and forms a separate layer with the residual paraiiinicconstituents when .treating a mixed base oil -of low asphalt Il' thenicconstituents and does not form a sepaents when treating a mixed base oilwhich is high in asphalt content or very high in content of naphthenicconstituents. Apparently, the nitrobenzene forms with asphalt ornaphthenic constituents a mixture having solvent power for parafnicconstituents. Another class of solvents, of which sulphur-dioxide is anexample, having a selective solvent power for naphthenic constituents,has a limited solvent power for constituents of mineral oil, dissolvespreferentially asphalts and those constituents of the oil which are ofhigher molecular weight, and has a definite selectivity for naphthenicconstituents. As illustrative of these properties, it has been foundthat when extracting a 17 A. P. I. residuum of California crudepetroleum obtained from Santa Fe springs, nitrobenzene gives anegligible yieldof paraflinic oil because of the high solubility of theentire residuum in the nitrobenzene; and

extracting of the same residuum with sulphurimproved results can beobtained, without preliminary precipitation and removal of asphalt, bycounterflowing a paraffinic solvent and a naphthenic solvent which has abroad or general solvent power for all types of naphthenic oils,including naphthenes and asphaltenes, and which has a capacity todissolve all non-parainic constituents o f the oil as Well as someparaffinic oil, and by introducing the oil to be treated to saidcounter-flowing lsolvents at a point above the point where freshparafnic solvent is introduced, so that the fresh paranicsolvent washesthe naphthenic -extract just before it leaves the system, asdistinguished from a process in which the oil to be treated is merelydiluted with a light hy'-` drocarbon diluent and the diluent oil iswashed with naphthenic solvent..

By employing a naphthenic solvent which is capable of dissolving all thenon-paraliinic constituents of the oil, including the asphalt and othernaphthenic constituents, and, in addition, some of the parafnic oil, andby operating in the manner just described, -the qualityv of the oilwhich is left in the upper or r'aflinate layer is greatly improved by.the removal of all of the undesired constituents, and, on the otherhand, a maximum yield of good oil is obtained by the Washing of theextract with fresh solvent for paraflini'c oil.

More specifically, by using nitrobenzene `or the like as thenaphthenic'solvent, and by introducing the oil to be treated to thepresence of this naphthenic solvent, as distinguished fromfirst dilutingthe oil with a light hydrocarbon diluent,

it is possible to separate from the oil all the nonparainicconstituents, including asphalt, 'in a unitary operation, and withoutthe precipitation of solid asphalt, and by counter-fiowing theparaflinic solvent, particularly liquefied propane, to the naphthenicextract, there is an excellent recovery of `the desired `paraflinic oil.Other ex- .amples of broad solvents which have the capacity content,nitrobenzene takes up asphalt and naphents, in addition to some parainicconstituents',

are benzaldehyde and nitrotoluene, as distin-l guished from sulphurdioxide, furfural, pyridine and aniline, which have a limited solventpower for only certain constituents of mineral oil.

A feature of this invention is that treatment of mineral oil with anagent having selective solubility for naphthenic constituents, in thepresence of an agent having solvent power for parainic constituents maybe effected by maintaining counteriiow of said agents and introducingthe oil to the counterflow agentsat a point intermediate the points atwhich they are introduced, a further feature being that the solution ofparainic constituents is withdrawn from the resulting mixture at a pointon the samev side of the point at which the oil is introduced as is thepoint at which the naphthenic solvent is introduced, and the solution ofnaphthenic constituents is withdrawn from the resulting mixture at apoint on the same side of the point at which oil is introduced as is thepoint at which the paraiiinic solvent is introduced. Further features ofthis inventionare that the counterflow is assisted by the difference inspecific gravity between the extracting agents employed, and temperatureconditions promoting limitation of themutual solubility of thecounteriiowing agents may be maintained by regulation of pressure uponthe counterflowing agents; and the operation may be a continuousoperation ora batch operation or a batch operation having continuousfeatures.

A further feature of this invention is that solidification of anextracting agent may be avoided when the treating temperatures are belowthe solidification temperature thereof, by mixing with the extractingagent prior to its introduction to the infiuence of such temperatures aquantity of oil that will prevent such solidication, a further featurebeing that the oil so mixed is a fraction separated from one of thefinal oil products and having characteristics undesirable inconstituents of that product.

A further feature of this invention is that solidication ofwax-containing oil, as a result of temperatures employed in theextracting operation, is prevented by introducing into the oil prior toits introduction into the extracting operation ingredients withdrawnfrom the extracting operation which will prevent such'solidication. Theadded ingredients permit wax present to precipitate in particlesseparate from each other and from the oil, giving a mixture that isfluid and in which the oil is freev and ready to be acted upon by thesolvents.v

Other objects and features and advantages of this invention will Vappearfrom the detailed description of the several illustrative embodiments ofthis invention described hereinI for the purpose of assisting in theunderstanding of my invention with the intention that my invention isnot limited .to such embodiments.

In the drawing in which like reference characters indicate similarparts,

The gure shows diagrammatically apparatus embodying my invention andwhereby my process may be practiced, such apparatus includingtemperature controlling and solvent recovery features.

In the practice of this` invention, oil which isl aisasss which hasgreater solvent power for parafiinic than for naphthenic constituents.Usually the latter solvent comprises one or more hydrocarbons o theparafiin series, and it reduces the viscosity-of the more parafiinicfraction and Ifacilitates a more rapid and complete separation therefromby gravity of a solution of naphthenic constituents. Also, it is thoughtthat the advantages of this invention are due in part to a replacementby the parainic solvent, which is a parain hydrocarbon of such paramnicconstituents of the oil-as may be dissolved in the naphthenic solvent,the parnic solvent being readily recoverable from the more naphthenicfraction, and thus facilitating more complete recovery of the parainicconstituents oi the oil in andas the incre parainic fraction thereof. Inthe descrlption herein of apparatus embodying my invention, and wherebymy process may be practiced, all ofthe above-mentioned features of thisvvents at an intermediate point thereof.

invention and additional features are present, but it is to beunderstood that the separate use of the described features falls withinthe scope di this invention, although such features co-operate when usedtogether to produce the advantages of this invention.

Referring to Fig. 1, a counterilow of parailinic solvent and naphthenicsolvent is maintained through contacting o'r extracting elements vIlland il, and the oil to be separated into iractionsis introduced to thecounterowing sol- The operation will be described in connection with theuse of nitro-benzene having sulphur-dioxide .absorbed therein as thenaphthenic solvent and containing .refrigerant coill 23, and pipe 24, to

the bottom of absorberl I9, from which the residual gas is vvented byvent 25 or returned .by

pipe 2'6 and pump 21 to gas'holder 20. Nitrobenzene charged withsulphur-dioxide is passed valve 30 and closing valve SI, oxideabsorptionapparatus and step may be elim- Linated.

through mixer :32, heatexchanger 33, pipe 34, cooling `coil 35, andvpipe36, 'into-'the upper porfrom the bottom' of absorber I9 by pump 28through pipe 29 back to pipe I5. By opening the sulphur-di- Then thenaphthenic solvent passes tionfof extractor II.

'Propane-contained in tanks' l1 and 38 is by pumps 99 and 49' throughpipe 4Iy to pipe 42: and propane in tank 43, which may be initiallyfilled by make-@inlet 44, is passed by pump '45 through pipe 46 to'pipe42. Propane in pipe v42 passes through heat exchanger 41,. pipe ,49,

heat exchanger 49, pipe 50,' cooling coil ll, and

pipe 52, to the lower portion of -extractor I9. e

Oil to be separated into 'fractions is passed from tank 5:1, whichmaybesupplied by makes up inlet 54, by means of pump 55, pipe 59, mixer 5l,heat exchanger 58, pipe 59,'cooling coil l., and pipe 6I, to .the upperportion of extractor Ill.

-Contacting and extracting towers Iland Il.-

are provided' with any type of packing 6.2, such ilnic solvent, readilyoccurs.

as coke, bricks, or raschig rings, suitable for permitting contact ofthe oil and the solvents; and they are maintained completely filled withliquid. Pumps it, 39, 4ii45, and 55 maintain such vpressure within theextracting towers, and cooling. coils 35, 5I, and 60 maintain liquidsflowing to the towers I0 and II at such temperature that the liquids inthe towers do not vaporize and are at such temperature that separationof a solution of more naphthenic iraction from a solution of moreparainic fraction occurs. From the bottom of extractor ii there is drawnby pump 63 a quantity of the heavy fraction separating out in extractorII, and possibly a part of the lighter layer separating out in extractorit, depending upon the rate of operation of pump 63. Liquid so withdrawncornprises naphthenic constituents, naphthenic solvent, paramnicconstituents, and paramnic solvent, and it is passed through pipe b4,heat exchanger 58, and pipe 65, into pipe 5t, and mixed in mixer 51 withthe incoming oil to be separated. The oil to be separated may containwax and have a melting point between 85 F. and 90 F., necessitating theuse of a steam coil 66 in tank '53 in order that it may be in liquidform; but after admixture with the liquid withdrawn from the extractorby pump 63, the 'incoming oil may be chilled in cooling coil G0 to atemperature well below that at which the wax therein solldifles, andthen the wax solidies in particles separate from each other and separatefrom the oil, leaving the oil free to be acted upon by the selectivesolvents in extractors I0 and II. I

At the temperature maintained within extractors IB and II, the solventshave limited mutual solubility, and separation into an upperlayercomprising the more paraillnic fraction dissolved in the paramnicsolvent and containing some naphthenic solvent, and a lower layercomprising the more naphthenic fractionv dissolved in naphthenic solventand containing some paraf- The resulting upper layer passes from the topof extractor Il through pressure regulating valve 61 to evaporating tank68 containing cooling coils 35, 5I

.and 60. 'I'he pressure in tank 68, and therefore the temperaturetherein, is regulated by withdrawing therefrom vapor of parafllnicsolvent by compressor 69, the output of the compressor pass-y ingthrough condenser I0 into tank 43.

The more 'parafllnic fraction, partly freed'of parafllnicA solvent, ispassed from tank 68 by pump II toseparator 12. Naphthenic constitu. entsdissolved in naphthenic solvent and collecting in the bottom ofseparator 12 pass through heat exchanger 33, in which the temperaturethereof is raised, and then they pass through pipe 'Il into pipe I5 andare mixed with incoming naphthenic solvent in mixer 32. 'I'he separationin tank 12' occurs because the temperature f and concentrationofparalnic solvent therein are` Aboth lowerv than 'in the 4top oftowerII. Thus, naphthenic -constituents which are undesirable ingredientspf'the more parafiinic fraction are eliminated therefrom; and the oiladded to the incoming naphthenic solvent in pipe i5 permits'thereduction of the temperature thereto lncooling coil 36 to a temperaturewhichmay be below the crystallization point of the naphthenic solventwithout occurrence of such solidication or crystallization.

The upper layer in separator 12, `comprising the more'paraillnicfractionand solvents, passes *through-pipe 14,. heat exchanger 41,vaporizer naphthenic constituents.

plied by coil 94 vaporizes naphthenlc solvent.'

which passes through condenser 95 to tank I2.

'Iar collecting in the bottom of extractor I0 and constituting the morenaphthenic fraction dissolved in naphthenic solvent and containing someparalinic solvent, is withdrawn from extractor |0 by pump 96 and passedthrough pipe 91, heat exchanger 49, vaporizer 98, pipe 99, vaporizer|00, pipe |0|, pipe 9, vaporizer |02, pump |03, and pipe |04, tonaphthenic run-down tank |05, from which naphthenic oil or tar may bewithdrawn through pipe |06. In heat exchanger- 49, paraflinic solvent iscooled preparatory to further cooling in coil 5|, and the extent ofcooling of paraffnic solvent may be regulated by adjustment of valve |01in pipe 50 and by-pass valve |08. In vaporizer 98, the heat of coil |09vaporizes paraffinic solvent, which passes to liquefying condenser |I0and then to tank 31.'

In vaporizer |00, the heat of coil II drives oi sulphur-dioxide, whichpasses by pipe ||2 to pipe 92.

If sulphur-dioxide or an equivalent ingredient is not employed,vaporizers 11 and |00 are eliminated by opening valves |I3 and closingvalves I I4. In vaporizer |02, the heat of coil I5 vaporizes naphthenicsolvent, which passes to condenser |I6 and then to tank I2. Pumps 1| and96 provide the pressure necessary for condensing parainic solvent incondensers 86 and H0, and the pressure on the fractions freed of propaneis released by valves |I1, and vacuum pump ||8 insures that naphthenicsolvent will be vaporized in vaporizers 19 and |02 at a temperaturewhich will not alter the same or the oil in contact therewith.

In the extraction step in towers I0 and the continuous upward flow ofparafnic solvent and the continuous downward' flow of naphthenicsolvent, preferably at temperatures at which the mutual solubility ofthose solvents is limited, carries upward parafiinic constituents of theoil and carries downward naphthenic constituents of the oil. Just priorto flow of parailinic constituents from the extracting step they arewashed with naphthenic solvent, and just prior to flow of naphthenicconstituents from the extracting step they are washed with parafnlcsolvent, which is a parailn and replaces parafhnic constituents of theoil which are dissolved in the solution of Apparently paraifinic solvententering by pipe 52 takes up naphthenic solvent which is released nearthe top of the extracting towers because of the lower temperature there;and the released naphthenic solvent moves downward and takes up oilconstitutents, thus giving a circulation Within the extracting towerswhich aids the freshly supplied naphthenic solvent.

Other ways of carrying out my invention, and other types of apparatus,are illustrated in my Patent No. 2,083,511 granted June 8, 1937, whichembodies subject matter divided from the present application. y

15, pipe 16, vaporizer 11, pipe 18, pipe 16, vapor- In the practice ofthis invention, the oils treated will preferably be viscous oils, i. e.,oils having a Saybolt universal viscosity of upwards of 50 seconds at100 F., including distillates and residues and mixtures thereof. Bytreatment in accordance With this invention, oils having characteristicscomparable to or better than the characteristics of similar oilsproduced from Pennsylvania crude petroleum may be readily produced fromoils from almost any eld, including particularly Mid-Continent andcoastal elds, it being an important feature of this invention that oilshaving such desirable characteristics can be produced from oils having ahigh content of asphalt, in some cases so high that treatment thereofwith a single solvent is impracticable In the production of oils inaccordance with this invention, preliminary acid treatment is notnecessary, although such a step may be performed; and the acid treatmentultimately required is markedly milder an'd more economical 'than acidtreatment required to attain the same degree of purification withouttreatment in accordance with this invention. For example, oil treated inaccordance with this invention may be brought to desired color by theuse of five to ten pounds of 98% sulphuric acid and ve percent of Palmclay; whereas the attainment of the same degree of purity withouttreatment in accordance with this invention requires as much as fifty`pounds of such acid, and also a heavy treatment of clay, per barrel ofoil.

Oils constituting the' more parainic fraction obtained by the practiceof this invention are dewaxable by known methods to produce oil of anycommercially desirable A. S. T. M. pour test. the type of wax-removalemployed, i. e., filterpressing or by difference of specic gravity,being so chosen as to be well suited to removal of the wax precipitatedby chilling. Moreover, when the solvents employed in the treatment ofoil in accordance with this invention include sulphur dioxide, the upperlayer of the separation, containing oil, naphthenic solvent, andparainic solvent, is well adapted to dewaxing processes, the sulphurdioxide acting to limit the wax remaining in solution after chilling andacting to prevent crystallization of the naphthenic solvent, relativelymild chilling (-,10 F.) being `required to obtain oil of 0 F. pour test.

f in liquid form, a pressure much higher than is necessary to maintainliquidity. For example, in the contacting and extracting zones orelements of theapparatus, pressures as high as 160 pounds may bemaintained in connection with the use of propane. Thus, in the apparatusreferred to in the drawing, successful operation* has been effected bymaintaining the pressure in the neighborhood of 160 pounds in thecontacting or extracting elements. In Fig. 1, such pressure may bemaintained in towers I0 and Il while tower I0 is at 75 F. 4and tower Ilis at about 50 F., while the pressure inA receiver 43 is about pounds,all pressures being gauge pressures unless otherwise specied.Waxv-containing oil may be maintained at such temperature as will insurecomplete fluidity thereof,

e. g., 135 F. to 145 F., prior to introduction into the system.Subatmospheric pressure may be maintained, with or without simultaneoususe of neutral substances acting to increase vapor pressure of thesolvents, for the purpose of eecting the driving oi or evaporation ofsolvents without decomposition of the solvents or of the oil; forexample, evaporation of nitrobenzenemay be eected by maintaining in tankl2 an absolute pressure in the neighborhood of l2 mm. of mercury.Sulphur-dioxide absorbed in naphthenic solvent may be maintained atatmospheric pressure and absorption effected at such pressure, theabsorption temperature being in y nitrobenzene containing absorbedsulphur-dioxide, an eifective separation temperature is F.10 F. Whenused with nitrotoluene, an eiective separation temperature is 15 F.

Procedure in accordance with this invention produces a fraction .moreparailnic than-the original'oil and which n: an oil having moredesirable characteristics than the original oil,y

anda fraction which is more naphthenic than the original oil and whichcontains the asphalt occurring in the-original oil and-is an asphalthaving valuable commercial properties. The oil obtained represents asubstantially greater yield than the yield resulting from the mere useof a naphthenic solvent. and the oil possesses equal orbetterharacterstics than an oil produced by the mere use of a naphthenicsolvent. For the purpose of illustrating the effect and results ofprocedure in accordance with this invention, various specific examplesare herein described, with the understanding that this invention is notin any respect limited thereto but is amplied thereby. l

Employing as the oil tobe treated a `stock comprising a residue obtainedfrom Sante Fe Springs, California, crude oil and having thecharacteristics given below, that stock was subjeoted to treatments asvfollows:

A. The stock was subjected to acid treatment in accordance with goodrefinery practice, using fty pounds of 98% sulphuric acid per Ibarrel ofstock, and the resulting acid sludge (hereinafter referred to asasphaltum loss) was drawn on and the oil was treated with pound of Palmclay per gallon by the .so-called Vcontact l method. I

C. The stock was treated with three pounds. of nitrobenzene per pound ofstock, but no separation was obtained at any temperature down to 30 F.,presumably because of the high asphalt content of the stock.

D. The stock was treated with one pound of nitrobenzene and two poundsof propane per pound of stock, the separation of the solution of morenaphthenic fraction beingeffected at 75 F., and the separation of themore parafnic fraction being eiectedat 35 F.,'under 60 pounds pressure.

E. The stock was treated with one pound o nitrobenzene and four poundsof propane per pound of stock, the separation conditions being asdescribed in test D.

F. The stock ,was treated withtwo pounds of nitrobenzene and four poundsof propane per pound of` stock, the -separation conditions being asstated in test D.

G. The stock was treated with twopounds of nitrobenzene and two poundsof propane per pound of stock, the separation conditions being as intest In order to compare the effect of treatment in accordance with thisinvention with other treatment, in connection with a less asphalticstock, tests were made with a stock of reduced asphaltic contentconsisting of the oil resulting vfrom test B, substantially freed ofasphalt by.

propane treatment, as follows:-

H. The stock of reduced asphalt content was treated with one pound ofnitrobenzene per pound of such stock, the separation temperature being50 F.

J. The stock of reduced asphalt content wasY treated with one pound ofnitrobenzene and two pounds of propane per pound of such stock, theseparation of the more paraffinic fraction being elected at 35 F. andthe separation of the naphthenic Afraction being effected at 75 F.

K. The stock of reduced asphalt content was treatedv with one pound ofnitrobenzene and twol tion freed of solvent.

. A. P. I. gravityI of the `resulting oil. Saybolt universal viscosityat 130 F. Saybolt universal viscosity at 210 F. Flash point in degreesF.

Fire test in degrees F. f Lovibond color, quarter inch cell.

. Conradson carbon. l

l0. Viscosity .gravity constant.

11. Viscosity index. -v

copo-:anywho:

loss of acid-treated oil or more naphthenic fracmil With respect to theasphalt or more naphthenic 'I fraction, there are given below:-

12. Specific gravity. 13. Melting point. 14. D uctllitY.

The average yields and characteristics `of products obtained in tests Ato G, employing Stanta F Springs residuum, and the ,characteristic ofthe'charging stock, as explained above, were as follows.'-

an amount per volume of solvent as has nitrobenzene, introducing the oilto be treated, con- The average yields and characteristics oi productshaving a ilash test of 450 F. and a lire test ofl 510 F. obtained intests H and J to N, employing oil of lower asphalt content, and thecharacteristics of the charging stocks, as explained above, were asfollows:

Stock H J K 1 100 so. 72. o 7o. 3 2 o 4s. 4 o 29. 7 3 21 25. 8 25. 2 25.5 4 505 304 245 301 5 sa 75 72 73 s Dark 13o 50 78 green 1o 851 .821 S25e30 11 50 92 12a 90 n both naphthenic and paraiiinic constituents.

From the foregoing, it appears that by the practice of this inventionproducts of highly desirable characteristics yare obtainable from oilsnot separable by the use alone of a practicable proportion of anaphthenic solvent and that this invention yields products having markedsuperiority over products obtained by use of naphthenic solvent alone.From the foregoing results, the effects of increasing and decreasing theproportionof the solvents to the oil and. to each other isindicatedsulciently to enable the operator to achieve the desiredresults; and it is demonstrated that the use of a parailinic solvent ashere- -in described results in marked increase of yield and markedimprovement of viscosity index. In

thepractice of this invention, the proportions of solvents may beextensively varied and the above results indicate the effects of suchvaria- .pha1t, which comprises counteriicwing a ,parafflnic solvent andva naphthenic solvent having a general solvent-power for all naphthenictype oils including naphthenes and asphaltenes, and hav-..-

ing a capacity to dissolve substantially as large Stock A B C D E F G 1100% 39% 82. 1% No separation 2 0% 61% 17.9 do 3 16. 8 25. 4 2l. 0 41430 297 506 5 168 72 89 445 450 450 7 505 510 510 S Black Dark greenDark green 4 9 0. 0 0. 7 10 885' 831 861 1l 42 86 60 12 Not recovered 1.074 13 d0 160 14 -do.. Brittle taining its entire asphaltcontent, tosaid counterflowing solvents at a point space from the point where freshparainic solvent is introduced, controlling the temperature of theextraction at a point where the parafnic and naphthenic solvent causethe oil to separate into layers, separating the layers and recoveringthe solvents from the separated layers.

2. Process as claimed in claim l wherein the parainic solvent is aliqueed normally gaseous hydrocarbon.

3. In a process for separating mineral oil containing paralnic andnaphthenic constituents into fractions respectively more paranic andmore naphthenic than the original oil, the steps comprising contactingthe oil with liquid propane and nitrobenzene, and separating theresultant solutions by difference of specific gravity, the said propaneand nitrobenzene being adapted to form a layer solvent system whencontacted with each other.

4. Process of refining mineral oil which comprises introducing the oilto be treated into nitrobenzene, withdrawing the resulting extract layercounterflow to liquid propane, and separating the pronane and oildissolved therein from the extract.

5. Method of solvent refining mineral oil without the need forpreliminary removal of asphalt,

which comprises counterflowing liquefied propane duced, separating aparaffmic raiiinate, and sep-v arating a naphthenic extractcountercurrent to fresh propane.

6. Method of solvent rening mineral oil without the need for preliminaryremoval of asphalt, which comprises counterfiowing substantiallyimmiscible paralnic solvent and a naphthenic solvent having a selectivesolvent power for all naphthenic type portions of the oil includingasphalt, said 'naphthenic solvent being capable of dissolvingsubstantially as wide a range and as large a quantity of said portionsand asphalt as does nitrobenzene, per unit of solvent, introducing theoil to be treated to said counterflowing solvents at a point above thepoint where fresh paraflinic solvent is introduced, separating aparaflinic raffinate, and separating a. naphthenic extractcountercurrent to fresh paraillnic solvent.

7. The method as claimed in claim 6 wherein said paraiilnic solvent isliquid propane.

8. Method of solvent rening mineral oil Without the need for preliminaryremoval of asphalt,

.which comprises counterflowing substantially immiscible paralnicsolvent and a naphthenic CERTIFICATE OF CORRECTIO Patent No., 2,155,555.

ing solvents at a point above the point where fresh vparainlc solvent isintroduced, separating a paramnic rafnate countercurrent to freshnaphthenic solvent, and separating a naphthenie extract countercurrentto fresh paramnic solvent.

MALCOLM H. TUTTLE.

April LL, 1959 MALCOLM H. TUTI'LE. VIt is hereby certified that errorappears in the printed specification of the abovenumbered patentrequiring correction as follows: Page 2, first co1umn,' 1ine' \8, for"diluent oil" read Vdiluted oil; page LIL, first column,` line 20, vfor"pipe 9" read pipe 99; and that the said Letters Patent should be readwith this correction therein that the same may conform to the record ofthe case inthe Patent Office.

signed and sealed this 15th day of June, A. D. 1959.,

(Seal) Henry Vari Aredale Acting Commissioner of Patents.-

